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Chapter 14

Bitmaps and Bitblts

A bitmap is a two-dimensional rectangular array of bits that correspond to the pixels of an image. When real-world images are captured in bitmaps, the image is divided into a grid and the pixel is the sampling unit. The value of each pixel in the bitmap indicates the average color of the image within a unit of this grid. Monochrome bitmaps require only one bit per pixel; gray shade or color bitmaps require multiple bits per pixel.

Bitmaps represent one of two methods for storing pictorial information in a Windows program. The other form of stored pictorial information is the metafile, which I'll cover in Chapter 18. A metafile is a description of a picture rather than a digital representation of it.

As I'll discuss in more detail shortly, Microsoft Windows 3.0 introduced something called the device-independent bitmap (DIB). I'll discuss DIBs in the next chapter. This chapter covers the GDI bitmap object, which is the bitmap support implemented in Windows prior to the DIB. As the various sample programs in this chapter demonstrate, the pre-DIB bitmap support of Windows is still quite useful and valuable.